France Curtails 6.4 GW of Nuclear Output as Heatwave Pushes River Temperatures Higher
EDF cut 14% of French power demand on Monday (2026-07-13) as river temperatures restricted reactor cooling, though France held its net export position.
France's nuclear fleet shed 6.4 gigawatts of output on Monday (2026-07-13) as a prolonged heatwave elevated river temperatures beyond the threshold at which reactors can legally draw cooling water, according to data reported by OilPrice.com. The curtailment represented 14% of France's total power demand that morning.5
The scale of the reduction matters for European power markets because France draws roughly 70% of its electricity from nuclear generation; when the fleet runs at capacity, France exports surplus power to its neighbours. RTE data showed France remained a net exporter despite the curtailments, with more than 10 GW flowing to neighbouring countries on Monday (2026-07-13) — a margin that absorbed the loss without triggering import dependency.5
Still, 6.4 GW simultaneously offline concentrates risk. Under tighter demand conditions, or if the curtailments extend past the current heatwave, less French nuclear output raises French wholesale prices, reduces the export surplus, and increases the call on gas-fired generation across the continent. ICE Endex TTF front-month was trading at €54.22 on Wednesday (2026-07-15), up 0.11% on the day, suggesting markets have not yet priced a prolonged outage scenario into European gas.5
River-temperature limits are a recurring constraint for EDF, not a structural surprise. The regulatory ceiling on cooling water discharge temperature means EDF must throttle output when rivers run warm and slow. Duration matters: heatwave-driven restrictions have historically persisted for days to weeks, and it is the sustained reduction rather than the instantaneous cut that shifts power market pricing.5
MetDesk had flagged this risk in May, identifying June as the period of highest seasonal probability for low river levels and elevated water temperatures capable of restricting reactor cooling, with drought adding further pressure on hydropower availability. The materialisation of that warning in mid-July (2026-07-13) confirmed the directional forecast, even if the timing arrived slightly later than MetDesk's peak-risk window.3
Against that operational backdrop, EDF's broader capital programme faces a separate regulatory pressure. The European Commission opened a formal investigation in May (2026-05-19) into France's plan to subsidise the construction of six new reactors with a combined capacity of 10 GW, at an estimated cost of EUR 73 billion in 2020 euros, Montel reported. Negotiations between Paris and Brussels are expected to run for months, the French economy and energy ministry told Montel. The probe adds uncertainty to EDF's expansion plans at precisely the moment the existing fleet's vulnerability to summer heat is visible in real-time generation data.1,4
EDF has separately argued that electrification is the correct strategic response to energy shocks. On Wednesday (2026-05-20), it announced a plan to lift French power demand by 5.5 TWh, or roughly 1% per year, with new heat pumps and electric trucks each targeted to contribute 0.5 TWh annually. The premise is that domestic electricity consumption, overwhelmingly nuclear-backed, reduces France's exposure to gas import costs. That logic is harder to sustain in periods when the nuclear fleet faces operational constraints driven by the same climatic conditions pushing up air-conditioning demand.2
The forward question is duration. River temperature forecasts over coming days will determine whether EDF can restore the curtailed capacity or whether additional units face restrictions as the heatwave persists. A sustained reduction lasting more than a week would begin to register in French day-ahead auction prices and, with a lag, in European gas benchmarks as backup generation competes for merit-order position. MetDesk's May analysis also flagged drought as a compounding risk: if reservoir levels drop in parallel with river temperatures, the backup generation pool narrows, and the 10 GW export buffer that held on Monday (2026-07-13) may not persist through the remainder of July.5,3